1、CEPT T/CS*20-15*E 81 2326414 0004532 B m: TCS20-15 Page 1 E Recommendation T/CS 20-15 (Innsbruck 1981) TONES AND ANNOUNCEMENTS Recommendation proposed by Working Group T/WG 11 “Switching and Signalling” (CS) Text of the Recommendation adopted by the “Telecommunications” Commission: “The European Con
2、ference of Postal and Telecommunications Administrations, considering - that in accordance with the principles outlined in Recommendation T/CS 20-01 i, the exchange and network features which are required for the implementation of services and facilities should be identified and specified; - that to
3、nes and verbal announcements are generally used to inform the customer of the progress of calls and are also suitable for the use and control of several new services and facilities, recommends to the members of the CEPT to recognise and introduce the feature tones and the feature announcements as de
4、scribed and specified below.” a 1. 2. 2.1. 2.2. 2.2.1. 2.2.2. 2.2.3. GENERAL Tones and announcements each belong to a special group of sound waves. Each tone and announcement transmitted from the network to the user is an audible indication of the network to the user. An audible indication is unders
5、tood to be a sound wave within the frequency range of 300-3,400 Hz, which is transmitted to inform the user, e.g. about the state of a telephone call or a supplementary service. The basic characteristics of an audible indication are the cadence, the frequency and the level. A mathemati- cal presenta
6、tion of tones and announcements is given in Annex 1 to this Recommendation. This Recommendation is compatible with the recommended multifrequency push-button signailing sys- tems 2. TONES FEATURE Definition The tones feature is defined as the ability of the network to send audible indications in the
7、 form of tones to the user. A tone is an audible indication comprising one or more discrete frequencies but excluding speech. Description In relation to cadence A continuous tone is a tone without cadence. An interrupted tone is a tone with cadence (Note 1). A tone burst is a relatively short tone w
8、hich occurs only once. In relation to frequency A pure tone is a tone having only one nominal frequency. A composed tone is a tone made up of more than one nominal frequency present at the same time. A multiple tone is a tone made up of more than one nominal frequency so that no more than one nomina
9、l frequency occurs at the same time. Note: Frequencies above 2,700 Hz should be avoided for tones. In relation to level A multi-volume tone is a tone having a changing level of volume. A discrimination of tones based on a change of level of volume should be avoided. Note: The studies on this series
10、p/CS 20) of Recommendations for the features in an analogue environment has now been terminated. A continuation of the studies has started with the aim to amend these existing features, where necessary, and to specify new features for the ISDN. These Recommendations will be gathered in a new series
11、of Recommendations. Note 1: In CCIT, the term infermitterit tone is used. m Edition of May 15, 1986 CEPT T/CS*ZO-LS*E 83 I 2326434 0004533 T 9 TICS 20-15 E Page 2 2.2.4. 2.2.5. 2.3. 2.3,l. 2.3.2. 2.3.3. 2.3.4. 2.3.5. Tone diagrams Diagrammatically tones may be shown as in Figure 1 (T/CS 20-15). Tone
12、 source A tone source is a device producing one tone. A generator producing a number of tones simultaneously is considered to be composed of the same number of independent tone sources. Technical characteristics The technical characteristics of tones are related to the electric phenomenon sent by th
13、e exchange to the user, and which, after transduction, becomes a tone. All measurements are made on the main distribution frame at the outgoing end of the exchange balanced by the required impedance standard. Continuous Toneburst - Pure - Composed - - - - Multiple - - Figure 1 (T/CS 20- 15). Tone di
14、agrams. Cadence Cadence is defined as a particular combination of tone pulse and pause times repeated in a cyclic manner. The pulse and pause times of a number of tones are harmonised at a single value as shown in the list of parameters below. The actual values should be kept within the tolerance li
15、mits of 10% of the nominal values. Frequency The frequency of tones is expressed in Hertz (Hz). The frequency of a number of tones is harmonized at a single nominal value as shown in the list of parameters below. The actual value of the frequency should in all circumstances be kept within the tolera
16、nce limits as mentioned in the list of parameters. Level The nominal level of the tone is expressed in dBm. The nominal level of a tone sent towards users should be adjustable to suit the subscribers line loss and the telephone characteristics of individual Administra- tions. The range of adjustment
17、 should be as shown in the list of parameters below. The level of a tone sent towards the trunk network should comply with current CCITT Recommenda- tions 3. Differences in the level of successive tones or tone components (and announcements) applied by the same exchange must not exceed 3dB after pso
18、phometric correction, not including silence or multi-volume tones. For exceptional reasons, it may be possible to introduce psophometric corrections that exceed this value. The application and removal of tones must not produce disturbing clicks. Purity All tones are defined as the sum of sinusoidal
19、signals. Other sound waves may accompany the tone. The signal to noise ratio shall not be less than 30dB, and the collective power of the other sound waves must not exceed 46 dBm (except for dial tone when MFPB is applied where the signal to noise ratio should not be less than 40dB). Distortion The
20、permitted level of harmonic distortion is included in the requirement concerning the collective power of other sound waves as given in 52.3.4. Edition of May 15, 1986 CEPT T/CS*20-L5*E 83 m 2326434 0004534 3 m i 2.3.6. 2.3.7. 2.4. 2.4.1. 2.4.1.1. 2.4.1.2. 2.4.2. 2.4.2.1. 2.4.2.2. TICS 20-1 5 E Page
21、3 Crosstalk The crosstalk attenuation between two circuits using common parts of the tone source shall be 2 50dB, in all circumstances, for frequencies in the 300-3,400 Hz band. List of parameters The following values are to be considered as nominal values in the long term. However, in the interim p
22、eriod, other values and characteristics may apply, but the long-term objective should be based on the values stated in Table 1 (T/CS 20-15). For levels, a nominal value should be chosen in the range shown below. The tolerance on the nominal level is +_ 3dB. Utilisation Possible uses of tones are lis
23、ted below. Call-related use of tones Connection set-up To advise the user: - to start dialling; - of the expiry of the maximum period for sending the next digit if the exchange recognises that insufficient - to wait for called party answer; - that the called party cannot be reached; - that the calle
24、d party is engaged. digits have been received; Tone Level Frequency Dial tone 425f15 -12 -8 Ringing tone 425$_15 -12 -8 Busy tone 425+15 -12 -8 Congestion tone 425k15 -12 -8 Special information tone -20 -16 1,400L-50 -20 -16 I 1, 1 -20 -16 Call waiting tone Intrusion tone Warning tone 1,400f50 -20 -
25、16 Pulse Pause 1,000 4,000 500 I 500 1,000 330 1,000 -I- 330 1,000 + Remarks Continuous pure tone 0.9 j ! I I CEPT T/CS*ZO-L5*E BL 2326414 OOOL1535 3 R Page 4 3. 3.1. 3.2. 3.3. 3.3.1, 3.3.1.1. 3.3.1.2. 3.3.1.3. 3.3.2. 3.3.2.1. 3.3.2.2. TICS 20-15 E ANNOUNCEMENTS FEATURE Definition Announcements are
26、defined as the ability fo the network to send the user an audible indication in the form of a recorded announcement. A recorded announcement is an audible indication in the form of speech. Description An announcer is a device which delivers one recorded announcement at a time. An announcing device d
27、elivering a number of recorded announcements simultaneously is considered to be composed of the same number of independent announcers. Technical characteristics The quality of recorded announcements is defined by a number of parameters which can be divided into two groups. The first group can be mea
28、sured with instruments; examples of these items are: the level, the frequency content, the signal/noise ratio. The second group can be qualified by means of subjective listening tests, panel scores, etc. Examples of these items are: intelligibility, recognisability, naturalness and intona- tion, Not
29、e: Care should be taken when connecting an MFPB receiver to a subscriber?s line to which an announcement is being sent. Technical mecrsurements All measurements are made on the main distribution frame at the outgoing end of the exchange, balanced by the required impedance standards. Level The nomina
30、l level of the recorded announcement is expressed in dBm. The nominal level of a recorded announcement should be adjustable to suit the subscriber?s line loss and telephone characteristics of individual Administrations. The level of the recorded announcement is measured by a speech peak level meter
31、having an upward integration time (= 0.7 full scale) of 2 ms and a downward integration time of 6 dB/s with Ri 20 kOhm. Variations in the nominal level of the recorded announcements as a result of fluctuations in temperature, variations in power supply, drift, load fluctuations or production toleran
32、ces, must not exceed 2. good; 3. fair; 4. poor; 5. bad. The results should be fair, good or excellent in 90% of the cases. - Edition of May 15, 1986 CEPT T/CS*20-L5*E 8L m 232b4L4 0004536 5 m TICS 20-15 E Page 5 3.4. Utilisation Using announcements, a large amount of different information can be off
33、ered to the telephone service users. The provision of announcements may involve more complexity and cost than tones., Note: See Annex 2 to this Recommendation for an example of a control interface between exchange and announcing device. Possible uses of the announcement feature are listed in the fol
34、lowing. 3.4.1. Call-related use 3.4.1.1. Connection Set-up To advise the user: - of a special condition on calling line; - of a special condition on called line; - that invalid information has been received; - that the system is faulty; - that there is a queue. 3.4.1.2. During the conversation To ad
35、vise the user: - of an intrusion; - that the conversation is being recorded. 3.4.2. Supplementary service related use 3.4.2.1. Control of a service O To advise the user: - to continue dialling; - that confirmation or rejection is required; - that more specific information is required; - of a fault c
36、ondition or lack of capacity. 3.4.2.2. During the use of a service - to provide the selected recorded announcement to the calling party; - to provide the selected recorded announcement to the called party. General designations of verbal announcements are detailed in Recommendation TICS 28-02 4. Oper
37、ational aspects of the utilisation of verbal announcements are dealt with in CCITT Recommendations E.181lQ.36 and E.182 5 and in Recommendation T/SF 14 6. References I 2 Recommendation T/CS 20-01. Exchange and network features. Recommendation TICS 46-02. Multifrequency signalling for push-button tel
38、ephones. Recommendation T/CS 46-03. Signalling system for push-button telephones combining multij?equency signals with direct current signalling. 3 CCITT Recommendation E. 18O/Q.35. Characteristics of the dial tone, ringing tone, busy tone, special information tone and warning tone. 4 Recommendation
39、 TICS 28-02. Names and meanings of tones and general designations of verbal announcements. 5 CCITT Recommendation E. 18114.36, Customer recognition of foreign tones. CCITT Recommendation E. 182. Application of tones and recorded announcements in telephone services. 6 Recommendation T/SF 14. Applicat
40、ion of tones and speaking announcements in telephone services. 7 CCIR Report 526. Edition of May 15, 1986 - . .% CEPT T/CS*20-L5*E 1 232bL1lL1 OOOL1537 7 W T/CS 20-15 E Page 6 ANNEX 1 Mathematical presentation of tones and announcements 1. GENERAL An audible indication may be considered to consist o
41、f m sinusoidal sound waves with frequencies f, fi, f,-, and respective amplitudes A, A, 9 A,_,. The sinusoidal sound wave with fre- quency fk is calledfrequency component k. For tones, m will be a small number (e.g. 1, 2 or 3) and the amplitudes A, (k = O, 1, m-1) are considered to be constant in ti
42、me. In order to be able to describe the rhythmical pattern of a tone, a cadence function C,(t) is attributed to each frequency component k, which describes at which intervals of time (tone pulses) the corresponding sound wave is present and where these intervals are located in time. For interrupted
43、and multiple tones, the cadence function is periodical with a period T which is defined so that it is equal for all frequency components. Per period, the frequency components may be present in different numbers of tone pulses with different time positions (this is particularly the case for multiple
44、tones). The tone pulses in which frequency component k is present are numbered O, 1, pk-1 from the beginning of each period. The tone pulse i of frequency component k starts after a time t, has elapsed from the beginning of each period and has a duration time of zki (see examples of key diagrams in
45、Section 4). Where the first period is considered to start at t = O, the presence of tone pulse i of frequency component k in all periods may be described as a pulse presence fimction Eki(t) by using forms of the step function E(t) as follows: 1-1 n=O Eki(t) = E(t-(tki+n.rc) - E(tki+Tki+nzc) Note: Th
46、e number 1 of periods depends on the application time of the tone. For a tone source, 1 may be considered to be infinite. Now the cadence function of frequency component k will be the sum of the pulse presence functions for all tone pulses in which this frequency component is present: =O For a compo
47、sed tone, all frequency components will have the same cadence function. A multi-volume tone may be described so that, in the tone pulses with different level, different frequency components are present with the same frequency value but with different amplitudes. A review of formulae for different to
48、nes is given in Section 2. It is theoretically possible to describe the sound wave of an announcement in the same way. However, the number of frequency components and the number of pulses per period will then be very large. It is, therefore, thought to be inappropriate to give a mathematical present
49、ation of announcements. 2. LIST OF FORMULAE 2.1. Audible indication: S(t) = Ck(t) . A, . sin(2nfkt) k=O 2.2. Continuous 2.3. Interrupted tone: C,(t) = 1 tone: C,(t) = T E,(t) =O I- n=O E,(t) = E(t-(t-(tk;fnzc) - + Tk; + .TC) E,(t) describes the presence of frequency component k in each cadence period 2.4. Tone burst: Ck(t) = f Eki(t) =O Eki(t) = E(t-t,) - E(t-(tki + T) 2.5. Pure tone: S(t) = C,(t) . A, . sin(2nfot) Edition of May 15, 1986 CEPT T/CS*20-15*E 81 = 2326434 0004538 9 T/CS 20-15 E Page 7 2.6. Composed 2.7. Multiple Ck
